diff --git a/app/src/main/java/com/example/tampopo_client/views/MainActivity.java b/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
index 983097b..a33fb60 100644
--- a/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
+++ b/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
@@ -383,7 +383,8 @@
 
         // すべてのフレンド（既存＋新規）に対してオブザーバーを登録
         for (String friendId : friends) {
-            MutableLiveData<List<Activity>> activitiesLiveData = activityViewModel.getActivitiesLiveDataFromUserId(friendId);
+            final String currentFriendId = friendId; // ラムダ式で正しく参照できるようにfinal変数にコピー
+            MutableLiveData<List<Activity>> activitiesLiveData = activityViewModel.getActivitiesLiveDataFromUserId(currentFriendId);
             
             // オブザーバーを登録（LiveDataは同じオブザーバーの重複登録を自動的に防ぐ）
             activitiesLiveData.observe(MainActivity.this, activities -> {
@@ -392,10 +393,10 @@
                 Activity latest = activities.get(activities.size() - 1);
 
                 // UIスレッドで安全に更新
-                FriendIconView friendView = userViews.get(friendId);
+                FriendIconView friendView = userViews.get(currentFriendId);
                 if (friendView != null) {
                     friendView.setComment(latest.getText());
-                    Log.d("ActivityUpdate", friendId + " のコメントを更新: " + latest.getText());
+                    Log.d("ActivityUpdate", currentFriendId + " のコメントを更新: " + latest.getText());
                 }
             });
         }